Throughout, eliminate argument to sig_dispatch_pending.

Throughout, eliminate argument to sig_dispatch_pending.
* exceptions.cc (setup_handler): Move non-interruptible condition handling
(back) to wait_sig (as suggested by Pierre Humblet).
(set_process_mask): Don't worry about calling sig_dispatch_pending from
sigthread since it is detected in the function anyway.
(sig_handle): Eliminate thisproc arg.  Don't call sig_dispatch_pending on
SIGCONT since that should happen automatically.
* sigproc.cc (sig_dispatch_pending): Eliminate justwake argument.  Just return
when called from sigthread.
(wait_sig): Change some variables to bool.  Change inner while to an if.  Move
uninterruptible signal handling here.
(sigproc_terminate): Don't call sig_dispatch_pending.  Just increment semaphore
on exit.
* speclib: Use slightly different (but still flawed) method for determining
symbols to extract from libraries.